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Cheng-Kai Liu, Chian-Yu Chiu, Stephen M Morris, Min-Cheng Tsai, Chii-Chang Chen, Ko-Ting Cheng
A linear-polarization rotator based on the optically tunable pitch of chiral-azobenzene-doped liquid crystals (CAdLCs) has been investigated. It is shown that the orientation of linearly polarized (LP) light can be optically tuned using CAdLCs and that the transmitted light possesses a good degree of linear polarization (DoLP). Experimental and simulation (4 × 4 Berreman matrix) results show that the rotation angle is dependent on the pitch as well as the number of turns of the cholesteric LC helix. Some causes to affect the DoLP of the output LP lights during photoisomerization are also discussed...
November 13, 2017: Materials
Michael Wegener, Mickel J Hansen, Arnold J M Driessen, Wiktor Szymanski, Ben L Feringa
The field of photopharmacology aims to introduce smart drugs that, through the incorporation of molecular photoswitches, allow for the remote spatial and temporal control of bioactivity by light. This concept could be particularly beneficial in the treatment of bacterial infections, by reducing the systemic and environmental side-effects of antibiotics. A major concern in the realization of such light-responsive drugs is the wavelength of the light that is applied. Studies on the photocontrol of biologically active agents mostly rely on UV light, which is cytotoxic and poorly suited for tissue penetration...
November 14, 2017: Journal of the American Chemical Society
Ammathnadu S Amrutha, K R Sunil Kumar, Takashi Kikukawa, Nobuyuki Tamaoki
Regulated transportation of nanoscale objects with a high degree of spatiotemporal precision is a prerequisite for the development of targeted molecular delivery. In vitro integration of the kinesin-microtubule motor system with synthetic molecules offers opportunities to develop controllable molecular shuttles for lab-on-a-chip applications. We attempted a combination of the kinesin-microtubule motor system with push-pull type azobenzene tethered inhibitory peptides (azo-peptides) through which reversible, spatiotemporal control over the kinesin motor activity was achieved locally by a single, visible wavelength...
November 16, 2017: ACS Nano
Philipp Weis, Wei Tian, Si Wu
Light can liquefy some solid azobenzene-containing polymers (azopolymers) via photoisomerization. Two types of photoinduced liquefaction of azopolymers have been reported: (1) Polarized light can guide solid azopolymers 'flow' along the polarization direction, which is called directional photofluidization and has been used for inscription of surface relief gratings (SRGs); (2) Recently, some of us found that light can switch the glass transition temperatures (Tg) of azopolymers and induce reversible solid-to-liquid transitions of these azopolymers...
November 8, 2017: Chemistry: a European Journal
Jenifer Rubio-Magnieto, Tuan-Anh Phan, Mathieu Fossépré, Valérie Matot, Jérémie Knoops, Thibaut Jarrosson, Pascal Dumy, Francoise Serein-Spirau, Claude Niebel, Sébastien Ulrich, Mathieu Surin
A new type of DNA ligand that contains a phosphate-binding group and a photoresponsive azobenzene moiety is reported. When the azobenzene is in trans configuration, the ligand binds to the minor groove of a double-stranded DNA, whereas it partially desorbs upon trans-cis isomerization with light. The ability to photoswitch the ligand upon interaction with DNA is evidenced by (chir)optical signatures, and deciphered by the differences of binding geometry, stability, and dynamics of the DNA/ligand complexes for the two isomers...
November 3, 2017: Chemistry: a European Journal
Mohammadreza Rezaee, Christopher P McNary, P B Armentrout
Protonated azobenzene (AB), H(+)(C6H5N2C6H5), has been studied using threshold collision-induced dissociation in a guided ion beam tandem mass spectrometer. Product channels observed are C6H5N2(+) + C6H6 and C6H5(+) + N2 + C6H6. The experimental kinetic energy-dependent cross sections were analyzed using a statistical model that accounts for internal and kinetic energy distributions of the reactants, multiple collisions, and kinetic shifts. From this analysis, the activation energy barrier height of 2.02 ± 0...
October 28, 2017: Journal of Chemical Physics
A Mohan Raj, V Ramamurthy
To probe the role of the supramolecular steric effects and free volume on photoreactions, geometric isomerization of neutral azobenzenes (ABs) and their radical ions, generated by electron transfer with gold nanoparticles, included within an octa acid capsule, was investigated. A comparison of the isomerization of ABs that proceed by volume conserving pyramidalization and stilbene analogues that proceed by volume demanding one bond flip has indicated the differing influence of 4-alkyl groups on these two processes...
October 30, 2017: Organic Letters
Shinjiro Sawada, Toshifumi Takao, Nobuo Kato, Kunihiro Kaihatsu
DNA carries genetic information in its sequence of bases. Synthetic oligonucleotides that can sequence-specifically recognize a target gene sequence are a useful tool for regulating gene expression or detecting target genes. Among the many synthetic oligonucleotides, tail-clamp peptide nucleic acid (TC-PNA) offers advantages since it has two homopyrimidine PNA strands connected via a flexible ethylene glycol-type linker that can recognize complementary homopurine sequences via Watson-Crick and Hoogsteen base pairings and form thermally-stable PNA/PNA/DNA triplex structures...
October 27, 2017: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
Oxana Kempf, Karl Kempf, Rainer Schobert, Elisa Bombarda
Dark fluorescence quenchers are nonfluorescent dyes that can modulate the fluorescence signal of an appropriate fluorophore donor in a distance-dependent manner. Dark quenchers are extensively used in many biomolecular analytical applications, such as studies with fluorogenic protease substrates or nucleic acids probes. A very popular dark fluorescence quencher is dabcyl, which is a hydrophobic azobenzene derivative. However, its insolubility in water may constitute a major drawback, especially during the investigation of biochemical systems whose natural solvent is water...
November 7, 2017: Analytical Chemistry
Chunyan Liu, Dong Zheng, Weigang Hu, Qiang Zhu, Ziqi Tian, Jun Zhao, Yan Zhu, Jing Ma
The combination of photo-responsive azobenzene (AB) and biocompatible Au nanomaterials possesses potential applications in diverse fields such as biosensing and thermotherapy. To explore the influence of azobenzene moieties and Au substrates on the collective switching behavior, two different azobenzene derivatives (rigid biphenyl-controlled versus flexible alkoxyl chain-linked) and three different Au substrates (a planar Au(111) surface, curved Au102(SR)44 and Au25(SR)18 clusters) were chosen to form six Au@AB combinations...
November 9, 2017: Nanoscale
Rosaria Vulcano, Paolo Pengo, Simone Velari, Johan Wouters, Alessandro De Vita, Paolo Tecilla, Davide Bonifazi
The E/Z isomerization process of a uracil-azobenzene derivative in which the nucleobase is conjugated to a phenyldiazene tail is studied in view of its ability to form triply-H-bonded complexes with a suitably complementary 2,6-diacetylamino-4-pyridine ligand. UV-Vis and 1H-NMR investigations of the photochemical and thermal isomerization kinetics show that the thermal Z→E interconversion is four-fold accelerated upon formation of the H-bonded complex. DFT calculations show that the formation of triple H-bonds triggers a significant elongation of the N=N double bond, caused by an increase of its πg∗ antibonding character...
October 24, 2017: Journal of the American Chemical Society
Kristin Munkerup, Dmitri Romanov, Timothy Bohinski, Anne B Stephansen, Robert J Levis, Theis I Sølling
Light harvesting via energy storage in azobenzene has been a key topic for decades and the process of energy distribution over the molecular degrees of freedom following photoexcitation remains to be understood. Dynamics of a photoexcited system can exhibit high degrees of nonergodicity when it is driven by just a few degrees of freedom. Typically, an internal conversion leads to the loss of such localization of dynamics as the intramolecular energy becomes statistically redistributed over all molecular degrees of freedom...
November 7, 2017: Journal of Physical Chemistry. A
Jiangang Feng, Qian Song, Bo Zhang, Yuchen Wu, Tie Wang, Lei Jiang
Deterministic assembly of nanoparticles with programmable patterns is a core opportunity for property-by-design fabrication and large-scale integration of functional materials and devices. The wet-chemical-synthesized colloidal nanocrystals are compatible with solution assembly techniques, thus possessing advantages of high efficiency, low cost, and large scale. However, conventional solution process suffers from tradeoffs between spatial precision and long-range order of nanocrystal assembly arising from the uncontrollable dewetting dynamics and fluid flow...
October 23, 2017: Advanced Materials
Nicholaus Prasetya, Bradley P Ladewig
In this paper, we demonstrate the highly efficient photo-switching ability of a Cu-azobenzene tetracarboxylate MOF (JUC-62) for low-energy CO2 capture. Under UV light irradiation, both at 273 and 298 K, JUC-62 showed 51% and 34% lower CO2 uptake, respectively, than when UV light was off. Its dynamic CO2 uptake also matched well with its static condition. Storing it at ambient condition was also found not to destroy its framework structure and its dynamic photoswitching property could still be maintained.
October 17, 2017: Scientific Reports
Masahiro Fujiwara, Masaki Kikuchi
The production of purified water by seawater desalination is now a significant countermeasure against recent severe water shortage. As the global warming is thought to be a dominant cause of the water scarcity problem, the energy employed for the desalination should be free from fossil fuels. We recently reported a simple membrane desalination combining the harvesting of solar energy and the membrane permeation of vaporized water. Water on a PTFE (polytetrafluoroethylene) membrane modified with disperse red 1 (DR1) as an azobenzene dye that photo-isomerizes with visible light permeates through it under visible light irradiation...
October 9, 2017: Water Research
Z Ahmed, A Siiskonen, M Virkki, A Priimagi
We present a series of visible-light-absorbing azobenzene photoswitches with cis-lifetimes ranging from one second to three days. We combine ortho-fluorination to control the cis-lifetimes, and ortho-amination to boost the visible-light absorption. The synthesis is accomplished by selectively replacing one or more ortho-fluorines with amines in the ortho-fluoroazobenzene precursors.
October 13, 2017: Chemical Communications: Chem Comm
Andreas Rennhack, Elena Grahn, U Benjamin Kaupp, Thomas K Berger
The voltage-gated proton channel Hv1 is expressed in various human cell types, including macrophages, epithelial cells, and sperm. Hv1 opening leads to proton efflux that alkalizes the cytosol. Here, we describe light-activated Hv1 inhibitors (photoswitches) that allow controlling its activity with high spatiotemporal precision. The photoswitches comprise a light-sensitive azobenzene moiety and 2-guanidinobenzimidazole (2GBI), a known Hv1 inhibitor. In the dark, photoGBI inhibits heterologously expressed Hv1 channels...
November 7, 2017: ACS Chemical Biology
Wibke Bronsch, Thomas Moldt, Larissa Boie, Cornelius Gahl, Martin Weinelt
Self-assembled monolayers of azobenzene-functionalized alkanethiolates form molecular ensembles with preferential orientation and significant excitonic coupling among the azobenzene chromophores. We have studied their optical switching with differential reflectance and two-photon-photoemission spectroscopy tuning the excitation wavelength through the excitonically broadened S2 absorption band. While the effective isomerization cross-section increases towards shorter wavelengths, the fraction of cis molecules in the photostationary state decreases...
October 12, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Andreas N Baumann, Michael Eisold, Arif Music, Geoffrey Haas, Yu Min Kiw, Dorian Didier
Spurred on by the recent emerging interest from the chemical community for unsaturated four-membered heterocycles, an unprecedented approach to nitrogen-containing four-membered rings has been designed. 3,4-Disubstituted 2-azetines were synthesized from commercially available substrates, allowing for a straightforward access to a new library of chiral functionalized azetidines and amino alcohols. This original approach was applied to efficiently prepare functionalized azobenzenes, an emerging class of molecules with a large potential in photopharmacology...
October 4, 2017: Organic Letters
Santosh Yadav, Smriti R Deka, Kunjlata Tiwari, Ashwani K Sharma, Pradeep Kumar
Self-assembled nanoformulations have been finding various applications in biomedical sciences. Here, we have designed and synthesized a small molecule based amphiphilic conjugate of azobenzene, Azo-PEG-OMe, which self-assembles into nanostructures in an aqueous environment. The formation of nanostructures was evidenced by light scattering and electron microscopic analyses which revealed the size of the so formed nanostructures ~199 and ~42 nm, respectively. Responsiveness of these nanostructures to various stimuli was demonstrated by enzyme and UV-Vis light exposure, pH and chemical reductant, sodium dithionite...
September 29, 2017: IEEE Transactions on Nanobioscience
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